This project will evaluate the effect of removal of large numbers of peripheral blood mononuclear cells in patients with severe rheumatoid arthritis. Vascular access will be obtained by forearm arteriovenous fistula and lymphopheresis performed three times weekly for 10 weeks using a continuous flow cell separator. The removed cells will be studied for membrane characteristics and in vitro assays of immune function. The clinical activity of the arthritis will be quantitated by a global activity index during and following completion of the project.